vp_vdpa: report doorbell address

stable inclusion
from stable-v5.13
commit 526cb858
category: feature
bugzilla: https://gitee.com/openeuler/kernel/issues/I5WXCZ
CVE: NA

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=526cb8580bc6b9e5bc14cc5d24ecf4633a84cfa1



----------------------------------------------------------------------

This patch reports the per vq doorbell location and size to vDPA
bus. Userspace can then map the doorbell via mmap() via vhost-vDPA bus
driver.

Signed-off-by: Jason Wang <jasowang@redhat.com>
Link: https://lore.kernel.org/r/20210415073147.19331-8-jasowang@redhat.com


Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Reviewed-by: Eli Cohen <elic@nvidia.com>
Signed-off-by: Pengyuan Zhao <zhaopengyuan@hisilicon.com>